Transcript Document

Chapter 14
Simulation and Other
Applications
What Is Simulation?
Simulation
A model of a complex system and the experimental
manipulation of the model to observe the results
Systems that are best suited to being simulated are dynamic,
interactive, and complicated
Model
An abstraction of a real system
It is a representation of the objects within the system and the
rules that govern the interactions of the objects
2
Constructing Models
Continuous simulation
– Treats time as continuous
– Expresses changes in terms of a set of
differential equations that reflect the
relationships among the set of characteristics
– Meteorological models falls into this category
3
Constructing Models
Discrete event simulation
Made up of entities, attributes, and events
– Entity The representation of some object in
the real system that must be explicitly defined
– Attribute Some characteristic of a particular
entity
– Event An interaction between entities
4
Queuing Systems
Queuing system
A discrete-event model that uses random
numbers to represent the arrival and
duration of events
The system is made up of
– servers
– queues of objects to be served
5
Please
wait!
Queuing Systems
To construct a queuing model, we must know
– The number of events and how they affect the system
in order to determine the rules of entity interaction
– The number of servers
– The distribution of arrival times in order to determine if
an entity enters the system
– The expected service time in order to determine the
duration of an event
6
Meteorological Models
Meteorological models
Models based on the time-dependent partial
differential equations of fluid mechanics and
thermodynamics
Initial values for the variables are entered
from observation, and the equations are
solved to define the values of the variables
at some later time
7
Meteorological Models
8
Meteorological Models
Computer models are designed to aid the
weathercaster, not replace him or her
– The outputs from the computer models are
predictions of the values of variables in the
future
– It is up to the weathercaster to determine
what the values mean
9
Meteorological Models
Relocatable models
Models applied to a moving target
Can you think of an example?
What is special about weather models?
10
Hurricane Tracking
(GFDL)
Geophysical
and Fluid
Dynamics
Laboratory
Figure 14.2
Improvements in
hurricane models
11
Graphics
Graphics
Originally the language of communications for
engineers, designers, and architects
Computer-aided design (CAD)
A system that uses computers with advanced
graphics hardware and software to create
precision drawings or technical illustrations
12
Graphics
Figure 14.3
Geometric
modeling
techniques
13
Graphics
Shape and surface influence an object’s
appearance
Equations used to describe planes, spheres,
and cylinders
Real world surfaces are rough, which scatter
light differently, requiring texture mapping
techniques
14
Graphics
Illumination model
Simulation of light interaction at one point
on an object
Shading model (shading)
Process of using an illumination model
to determine the appearance of an
entire object
Rendering
The process of creating an entire image
15
Modeling Complex Objects
Figure 14.5 A natural computer generated landscape
16
Modeling Complex Objects
Figure 14.6 Midpoint subdivision
for creating fractal terrains
17
Modeling Complex Objects
Figure 14.7 Water pouring into a glass
18
Modeling Complex Objects
Figure 14.8 Cellular automata-based clouds
19
Modeling Complex Objects
Figure 14.9 A campfire
20
Modeling Complex Objects
Figure 14.11 A simulation of cloth showing ending and draping
21
Modeling Complex Objects
What is the most difficult object to model?
22
Embedded Systems
Embedded systems
Computers that are dedicated to perform a narrow
range of functions as part of a larger system
Empty your pockets or backpacks.
How many embedded systems do you have?
23
E-Commerce
Electronic commerce
The process of buying and selling products
and services using the WEB
Can you name at least 3 e-commerce sites
that you have visited lately?
What made e-commerce feasible and easy?
What problems does e-commerce face?
24
Computer Security
Authentication credentials
Information users provide to identify themselves
for computer access
• User knowledge name, password, PIN
• Smart card card with embedded memory
chip used for identification
• Biometrics human characteristics such as
fingerprints, retina or voice patterns
25
Computer Security
Malicious Code
A computer program that attempts to bypass appropriate
authorization and/or perform unauthorized functions
Worm stand alone, targets network resources
Trojan horse disguised as benevolent resource
Virus self-replicating
Logic bomb set up to execute at system event
26
Computer Security
Security Attacks
An attack on the computer system itself
Password guessing obvious
Phishing trick users into revealing security
information
Spoofing malicious user masquerades as authorized
user
Back door unauthorized access to anyone who
knows it exists
27
Computer Security
Buffer overflow defect that could cause a system to
crash and leave the user with heightened privileges
Denial-of-service attack that prevents authorized
user from accessing the system
Man-in-the-middle network communication is
intercepted in an attempt to obtain key data
Have you ever experienced one of these?
28